I am having the same issue. I have been 100% completely fine until this last patch. It's a mess, I try to start my last mission "Killing Kane" and I cannot get to the freaking mission , "Fatal" is all I get. I'm an IT developer what jack-wagon 3rd party out-sourced development puts "Fatal" and no error on the screen. You can't even research it, there isn't an damn error.

The problem would be that the recent patch broke most if not all existing mods. Which is normal if you ever played a game with mods that is still being patched. Either disable your mods or wait for the authors to update their mods. Baradul will most likely face the same issues at the moment.

Here's info directly from the patch notes.
- It details a new simpler and easier method for Mod makers to add their Mods, without changing core game elements.
- Adds a new Mods element in the main Game window.
- Adds updated path finding for your Ai Pilots so they don't walk through your mission "to save" city.
- Adds support for the new Nvidia DLSS 2.0 (for RTX GPU's)

Patch Date and Time - 23 MAR 2020 @ 10 AM PDT
Patch Number: 1.0.227
Welcome to the latest MechWarrior 5: Mercenaries Mod Editor and game update! This update focuses on introducing a significant array of improvements to in-game Mod support and the Mod Editor, along with general game improvements for AI obstacle avoidance and the addition of a news carousel to the Title Screen.

Prior to release of this update we strongly recommend that all Mod makers disable the Epic Games Launcher auto-update feature for the MechWarrior 5 Mod Editor and back-up all your modded assets (in their pre-cooked form!). We cannot stress enough how important this is, as any modifications you’ve made to existing game content is likely to be overwritten by this update. You will also need those backups to port your work into the new system.
The new mod creation framework introduced in this update will greatly help to mitigate these kinds of conflicts in any future updates. This update will eliminate the need to directly modify source game assets, and instead introduces a semi-automated system for making safe, mod-specific duplicates of any asset you want to modify.
When it comes to packaging your Mod, this update also introduces a simple one-button solution to handle what had previously been a convoluted and error-prone manual process for cooking and packaging your mods. No more custom bat files and inflated cook times!

Our Mod Editor Guide has been updated to reflect the new system for creating and packaging your Mods. It also includes steps for porting your previously built Mod into the new system.

In addition to the built-in support for creating and packaging your Mods, this update features an array of improvements to the number of core systems exposed to modification.
On the game side you'll see a new Mods option available in your Title Screen, which will bring you to a new interface for managing your installed Mods. Important note: Mods must have been built under the new system introduced in this update in order to be compatible with this screen. Any mods that were manually cooked and packaged by the author and distributed as a basic PAK file will not appear in this screen.
- The MechWarrior 5 Team

Game Updates

A Mod Manager screen has been added to the Title Screen, providing support for the enabling and disabling of installed Mods that were built in this latest version of the Mod Editor.

AI obstacle avoidance has been improved, making them less likely to walk through buildings and other destructible objects.